1. Field of Invention
The present invention relates to an inkjet printer, and more particularly to an inkjet printer capable of adjusting the distance between a printhead module and a printing medium.
2. Related Art
Generally, an inkjet printer jets ink onto a printing medium to print a picture. The distance between a printhead module and the printing medium should be kept at a constant level, so as to optimize the printing quality. When the above distance becomes smaller, the ink jet range is shortened, and the jetted ink spots (i.e., pixels) are getting smaller and denser. Thereby, a greater number of pixels can be printed on the same area, and a better picture quality is achieved. On the contrary, if the distance is enlarged, the printed pixels become smaller. When the distance gets too large, the shape of the pixel is deformed, and the quality of the printed picture will be degraded. Likewise, if the distance is too small, the printing quality may also be affected. For example, if the printhead module gets too close to the printing medium, the wet ink on the printing medium may be passed on to the printhead module, and especially when moving back and forth, the printhead module again applies the ink onto the printing medium, thus seriously affecting the printing effect.
Recently, the distance between the printhead module and the printing medium in the inject printer is mainly adjusted by an assembly engineer during the printer assembly process according to experience. The engineer first uplifts the printhead module to a certain height with a jig, then confirms that the distance between the printhead module and the printing medium is reasonable after several times of debugging and inspection, and finally fixes the printhead module. During the debugging and inspection process, as the distance between the printhead module and the printing medium is mainly controlled by the assembly engineer according to experience, the accuracy is low and the debugging requires a lot of time and effort.
In Taiwan Patent No. 491188, a technical solution of adjusting the distance between the printhead module and the printing medium is disclosed. A carrier platform for carrying the printing medium serves as an adjusting object, i.e., the printing medium moves up and down with the carrier platform, so as to adjust the distance. However, this adjusting manner changes the medium path, and thus potential problems may occur during the movement of the medium in the printer, for example, the paper may be easily jammed during the printing process.
In addition, some other technical solutions are also provided to solve the problem of the distance between the printhead module and the printing medium during the printing process of the inkjet printer. For example, in PRC Patent No. 200710160332 disclosed on Jun. 25, 2008, an inkjet printing device and a method thereof are disclosed to achieve a constant distance between the printhead module and the printing medium by adjusting the height of the printhead module. However, this adjusting manner is complicated and of a high cost.
Therefore, it is in urgent need of a technical solution simple in structure, low in cost, and capable of effectively adjusting the distance between the printhead module and the printing medium, so as to improve the printing quality.